drylock

I am having a bit of trouble with some sections of great stuff in my build. The surface of the spot is really rough and pitted, to where it will be quite difficult to get an even or complete coat of drylock onto. I have tried carving and respraying but due to where the egg crate framework is...

I decided to use another method from grouting and water sealing to make some fake magnetic ledges. I purchased the drylok masonry waterproof gallon but the issue am having is it doesn't seem hardened even after 3 coats the styrofoam is still spongy. Any suggestions?

I have been searching the threads for a while gathering ideas on how to rebuild my 40 gallon Oceanic Hex once again. I finally decided on making a water feature and some trees with sheet foam and Drylock. My main motivation, besides getting lost in a fun project, is to make a low maintenance...